Liquid crystal light valve projectors have been used in the past for large screen projectors utilizing liquid crystal light valves or LCLVs to modulate the light being projected. For this purpose the LCLVs are selectively modulated by an appropriate apparatus such as cathode ray tubes (CRT). Such systems have used a first color separator responsive to unmodulated polarized light for reflecting light of a first primary color and for transmitting the remaining portion of the incident unmodulated polarized light and for internally reflecting incident light.
Various color separating apparatus are utilized to separate the primary colors for respective individual modulation. Dichloric mirrors have been utilized, but they tend to exhibit astigmatism and polarization sensitivity. Prisms have also been used for avoiding problems associated with dichloric mirrors. However, in view of the heat generated, such prism assemblies may suffer from stress by refringence if used in a projector. Accordingly, known liquid crystal light projectors could not utilize the advantages of color separating prisms having glass prisms or wedges and instead utilize other color separation structures which do not provide the same performance.
With regard to known liquid crystal light valve projections the respective color channels include unequal path lengths through the optical structure of the color separation apparatus. As a result, image quality is degraded.
Other known liquid crystal light valve projectors utilize both axes of polarization and are characterized by reduced contrast. Other systems utilize unmodulated polarized light with internal reflecting systems for separating colors into various primary colors. An example of such a system is shown in U.S. Pat. No. 4,687,301 issued to Ledebuhr on Aug. 18, 1987.
The problem with this type of system is that the resolution is not necessarily acceptable because of the effect of the filters. By using a modulator with high efficiency, according to Applicant's invention, a much better color projection system is obtained than has heretofore existed.
The apparatus or system which overcomes the problems discussed above include a white light source illuminating a dispersive element which angularly separates the light spectrum to provide different colors at different angles. This angularly dispersed light illuminates a lenticular lens array placed in front of a segmented spatial light modulator. Since the angle of the primary colors of red, blue and green are different they focus at different lateral positions behind the lenticular array. The array of light modulators is located so that each focused color spot illuminates a different modulating element. This results in three modulating elements for each of the lenticular lenses with data address to provide red, blue and green pixels located side by side. The elements are recombined on a projection screen by a single projection lens so that they are either resolved or they are blurred out using a defocus.